Epoxy polyurethane polyureas from epoxy resin, blocked isocyanate prepolymer and polyetherpolyamine

ABSTRACT

An epoxy polyurethane.polyurea product having improved impact properties is formed by reacting a curing amount of a polyetherpolyamine such as, for example, an amine terminated ethylene glycol with blends of epoxy resins combined with small amounts of blocked polyoxypropylene polyol/isocyanate.prepolymer. The products of the instant invention exhibit improvements over similar blends cured with other amine curing agents which result in brittle products.

FIELD OF THE INVENTION

This invention relates generally to epoxy curing agents. More particularly, this invention relates to amine curing agents and to novel epoxy polyurethane.polyurea products having improved properties which are formed by reacting an effective curing amount of a polyetherpolyamine with a blend of epoxy resin and a small amount of blocked polyoxypropylene polyol/isocyanate prepolymer.

The novel products of the instant invention exhibit improvements over similar blends cured with a variety of other amine curing agents known to result in brittle products. In particular, the use of amine terminated triethylene glycol as an amine curing agent provided low viscosity mixtures resulting in cured products with a very high degree of toughness and at the same time containing only a small amount by weight of blocked isocyanate prepolymer. The cured products are useful for coatings, sealants and encapsulating systems.

BACKGROUND OF THE INVENTION

It is known in the art to cure a blend of epoxy resin and blocked isocyanate prepolymer with an amine. For instance, in Mobay Product Information Bulletin "Desmocap 11A" such cures are described. In the Mobay literature, in an article titled "New Solvent-Free Epoxy/Polyurethane Combinations", Wellner, Gruber and Ruttman disclose information on properties exhibited for systems cured with Laromin C-260, isophorone diamine or trimethylhexamethylene diamine. Cycloaliphatic diamines were described as particularly successful.

A paper generated at the Kelso & Cibulas, SPI-ERF Meeting, Atlanta, Nov. 30, 1983 describes combinations of isocyanate prepolymers blocked with alkyl phenols and liquid epoxy resins which form stable mixtures. Such mixtures were quite reactive with amines. Amines cited were 3,3'-dimethyl-4,4'-diaminocyclohexylmethane (commercially available as Laromin C-260), bis(aminopropyl)piperazine, a polyglycol diamine and isophorone diamine. Properties given were those obtained with Laromin C-260.

In the related work in the art the products resulting from curing epoxy resin and blocked isocyanate prepolymer blends with amines are brittle materials with few redeeming characteristics. The amine curatives are often hindered amines.

It would be a distinct advantage in the art if a amine component could be used in a curing system which would allow for a product which was not brittle, but very tough and impact resistant and useful for producing flexible coatings, castings and sealants that cure rapidly at ambient temperatures. It would also be advantageous if the amines were effective using only small amounts of isocyanate prepolymer to yield products with desirable properties.

SUMMARY OF THE INVENTION

In accordance with the foregoing the present invention is directed to a polyurethane.polyurea composition which may be cured for extended periods at ambient conditions comprising an epoxy resin/blocked isocyanate prepolymer blend and a curing agent comprising a polyetherpolyamine. It has been surprisingly discovered that improved, desirable properties are observed in the cured product particularly where an amine terminated triethylene glycol is used as the curative of a liquid blend of epoxy resin/blocked isocyanate prepolymer. Further, only small amounts of isocyanate prepolymers are required in order to develop the improved properties. The invention is also a method for curing an epoxy resin/blocked isocyanate prepolymer blend with a polyetherpolyamine.

DETAILED DESCRIPTION

The polyetherpolyamine curatives for the present invention may include several different amines. In general, the polyetherpolyamines may be defined as polyetherpolyamines having one of the following formulas: ##STR1##

The polyetherpolyamines used as curing agents of epoxy resins blended with small amounts of blocked polyoxypropylene polyol/isocyanate prepolymer can be either polyoxypropylene or polyoxyethylene amines or combinations of both (See 3, above).

In general, the average molecular weight of a polyoxypropylene diamine curative will be from about 200 to about 6000.

One group of appropriate polyoxyalkylene diamines, containing both ethylene oxide and propylene oxide, which may be used are polyoxypropylene diamines having the formula: ##STR2## wherein a+c equals a number having a value of from about 2 to about 3 and b is a number having a value of from about 5 to about 45. The preferred amines include polyoxypropylene and polyoxyethylene or a combination thereof.

Suitable polyoxypropylene diamines have the general formula: ##STR3## wherein R' independently represents hydrogen or methyl and x is a number having an average value of 2 to 3. Such a polyoxypropylene diamine which is commercially available is JEFFAMINE® D-230 amine produced by Texaco Chemical Company.

Suitable polyoxyethylene amines include those having the formula:

    H.sub.2 N--(CH.sub.2 CH.sub.2 --O).sub.x CH.sub.2 CH.sub.2 NH.sub.2

where x=1, 2 or 3.

The examples demonstrate desirable improvements observed by curing a blend of epoxy resin and blocked polyoxypropylene polyol/isocyanate prepolymer with an amine terminated triethylene glycol having the formula:

    H.sub.2 N--CH.sub.2 CH.sub.2 --O--CH.sub.2 CH.sub.2 --O--CH.sub.2 CH.sub.2 NH.sub.2

and commercially available as JEFFAMINE® EDR-148 produced by Texaco Chemical Company.

It is quite unexpected that an amine terminated triethylene glycol, such as JEFFAMINE® EDR-148 amine, can be used as a curing agent of epoxy resin blends to obtain materials with improved properties. As the examples will demonstrate a low viscosity mixture having several outstanding properties was observed. For instance, the formulation exhibited a high degree of toughness as indicated by a high value for impact strength when only a small amount of blocked prepolymer was present in the blend.

Typical amines which have been used in the related art for curing epoxy resin/blocked isocyanate blends include Laromin C-260, 3,3'-dimethyl-4,4'-diaminocyclohexylmethane, a hindered cycloaliphatic amine available from BASF. Another recommended curative was bis(aminopropyl)piperazine. As will be demonstrated in the examples, both of the above-mentioned curatives form viscous mixtures and when cured form mixtures which are brittle and without strength.

However, the polyetheramines of this invention, especially JEFFAMINE® D-230 and JEFFAMINE® EDR-148 amine, formed low viscosity mixtures which after curing exhibited improved properties.

When JEFFAMINE® D-230, which is also a hindered amine, was used as a curative of the epoxy resin/blocked isocyanate blend the mixture had low viscosity but was very slow to react, although the properties of the product were desirable. This would indicate usage in areas such as filament winding, potting and encapsulation where an extended working time is necessary.

Quite unexpectedly the JEFFAMINE® EDR-148 resulted in a low viscosity mixture which reacted rapidly and resulted in a product with a very high value for impact strength, indicating a high degree of toughness. An additional desirable property was that it required the presence of only a small amount of blocked prepolymer. Adhesive properties were also improved. Such formulations would be useful in applications such as reaction injection molding, where rapidity of reaction is required.

The epoxy prepolymer blends used in the instant invention comprise blends of epoxy resins with small amounts of blocked polyoxyalkylene polyol/isocyanate prepolymer. The epoxy resin is typically one prepared by the reaction of Bisphenol A with epichlorohydrin in the presence of sodium hydroxide. After condensation is complete, the crude resin is freed of residual epichlorohydrin, washed well to remove salt and soluble by-products and recovered.

Curing of such a resin is accomplished in combination with a blocked isocyanate prepolymer and the polyetherpolyamine of this invention. Preferably the epoxy resin is a liquid. Among those which have demonstrated the effectiveness of the instant invention are diglycidyl ethers of Bisphenol A, such as liquid epoxy resin EEW≈185 (EEW=epoxy equivalent weight; molecular weight of resin=≈380; functionality≈2; equivalent weight≈185-190.

The blocked isocyanate prepolymer used in the instant invention comprises a polyoxyalkylene polyol/isocyanate prepolymer blocked with a phenol.

The blocked isocyanates used contain an average of 2-6, preferably about 2-4 blocked isocyanate groups per molecule and may be prepared from almost any organic polyisocyanate. It is preferred to use aromatic polyisocyanates such as the alkarylene polyisocyanates, e.g., 4,4'-diphenylene methane; 2,4 or 2,6 toluene or mixtures thereof; or 4,4'-toluidine or 1,4-xylylene diisocyanates.

Particularly preferred are the commercially available aliphatic, cycloaliphatic and aromatic diisocyanates. Blockage of the free isocyanate groups should be with phenol or preferably with an alkylated phenol. The use of a polyoxy propylene polyol/toluene diisocyanate reaction product blocked with nonylphenol is demonstrated in the examples.

In the instant invention only small amounts of isocyanate prepolymer are needed in order to develop enhanced properties. The amount of isocyanate prepolymer in the instant invention is from 5 to 50% by total weight of epoxy resin blocked isocyanate prepolymer blend. Less than 30% of isocyanate prepolymer by weight of total epoxy resin blocked isocyanate prepolymer blend is required. The examples demonstrate that the enhanced properties can be produced using 10 to 30% by weight of isocyanate prepolymer.

Practice of the novel method of this invention may be apparent from the description in Examples 1 through 7.

Examples 1 through 3 compare the polyetherpolyamine curatives with other amines used in the art. Examples 4-7 focus more on the particularly desirable properties obtained using amine terminated triethylene glycol.

The novel use of the non-hindered amine terminated triethylene glycol as a curative provides for the production of low viscosity mixtures which react rapidly to form materials exhibiting a high degree of toughness and improved adhesive properties. Uses for these products will be readily apparent to those skilled in the art and such products should be especially desirable in applications such as reaction injection molding because of the rapidity of reaction observed.

In the Examples of this invention the preparation of the cured resin blend is carried out in the following manner: The epoxy resin/blocked isocyanate prepolymer blend is reacted in a solvent free system with the polyetherpolyamine to provide solvent free unplasticized flexible compositions. After the amine curing agent is added, the mixture is mixed, degassed and poured into molds. Curing is for an extended period at ambient conditions.

In the various Examples the following properties are measured:

    ______________________________________                                         Tensile Shear Strength, psi - ASTM D1002                                       Brookfield viscosity, cps, ≈23° C. - ASTM D1824                 Gel time, mins. - ASTM D2471                                                   (200 g mass)                                                                   Rheometric Impact - High rate impact test - simulates actual                   impact failures at high speeds (Rheometrics).                                  Tensile Strength, psi - ASTM D638 - The rupture strength                       (stress/strain product at break) per unit area of material                     subjected to a specific dynamic load.                                          T-peel strength - ASTM D1876 - determines relative peel                        resistance of adhesive bond between flexible adherents.                        Tensile modulus, psi - ASTM D638                                                                  Stress  (psi)                                                                  Strain  (in/in.)                                            Flexural strength, psi - A measure of the ability of a material                to withstand failure due to bending. ASTM D790                                 Flexural modulus, psi - Stress/strain. ASTM D790                               ______________________________________                                    

It will be noted from Example 1 that Laromin C-260, which is a hindered amine, formed a viscous mixture that was slow to react with the epoxy blocked prepolymer. When cured for an extended period under ambient conditions, the mixture was brittle and without strength. Another recommended curative [bis(aminopropyl)piperazine] also produced a viscous mixture but was quite reactive and cured the blend to form a casting with adequate but somewhat brittle properties. JEFFAMINE® D-230, also a hindered amine, formed a low viscosity mixture with the epoxy blocked isocyanate blend but was very slow to react. Again, adequate properties were obtained. Quite unexpectedly, curing with a non-hindered polyetherpolyamine, JEFFAMINE® EDR-148 resulted in a low viscosity reactive mixture with several outstanding properties. A very high value for impact strength was found for this formulation indicating a high degree of toughness with only a small amount of blocked prepolymer present in the system. Adhesive properties of this formulation were also considerably improved over others of the series.

The Examples are given only in the way of illustration and are not to be regarded as limiting the invention.

EXAMPLE 1

    ______________________________________                                         Properties: Epoxy Resin/Blocked Isocyanate Prepolymer                          Blend (90/10 pbw) Cured With Various Amines                                    6297                                                                           Formulation:                                                                   17B                                                                            62B                                                                            19B                                                                            4A                                                                             ______________________________________                                         Liquid epoxy resin                                                                             90      90      90     90                                      (EEW ≈ 185)                                                            Blocked prepolymer.sup.1                                                                       10      10      10     10                                      3,3'-Dimethyl-4,4'-diamino-                                                                    30      --      --     --                                      cyclohexylmethane.sup.2                                                        Bis(3-Aminopropyl)-                                                                            --      23      --     --                                      piperazine (BAPP)                                                              Polyoxypropyleneamine                                                                          --      --      28     --                                      (MW ≈ 230).sup.3                                                       Triethylene glycol                                                                             --      --      --     18                                      diamine.sup.4                                                                  Exothermic Properties:                                                         Brookfield viscosity,                                                                          8500    4300    ≈2000                                                                         1200                                    cps, ≈23° C.                                                    Gel time, mins. ≈90.sup.7                                                                      30.0    ≈258.sup.7                                                                    36.4                                    (200 g mass)                                                                   Peak exothermic 115.0   219.5   33     236.5                                   temperature, °C.                                                        Time to peak tem-                                                                              190     39.0    414    39.7                                    perature, mins.                                                                Properties of Cured                                                                            6                                                              1/8 in. Castings.sup.5:                                                        Rheometrics impact,     4       15     126                                     total energy, in-lbs.                                                          Tensile strength, psi   8100    8700   8800                                    Tensile modulus, psi    344000  408000 414000                                  Elongation at break, %  2.7     3.3    3.2                                     Flexural strength, psi  13600   14700  14300                                   Flexural modulus, psi   404000  416000 420000                                  HDT, °C., 264 psi/66 psi                                                                        57/58   44/47  48/50                                   Adhesive Properties.sup.5:                                                                     8                                                              Tensile shear strength, psi                                                                            1300    1400   3050                                    T-peel strength, pli    3.5     5.1    9.4                                     ______________________________________                                          .sup.1 Polyoxypropylene polyol/TDI reaction product block with                 nonylphenol; Desmocap 11A (Mobay Chemical Corp.)                               .sup.2 Laromin C260 (BASF)                                                     .sup.3 JEFFAMINE ® D230                                                    .sup.4 JEFFAMINE ® EDR148                                                  .sup.5 Cured 14 days, ≈23° C.                                   .sup.6 Casting brittle; without strength. Shattered on removal from mold       .sup.7 Time to reach 10,000 cps                                                .sup.8 Brittle adhesive bond. Fractured before testing. No properties          could be determined.                                                     

In Example 2, using 20 parts by weight blocked isocyanate prepolymer per total epoxy resin the trends in the data were similar to those found in Example 1. Laromin C-260 formed a brittle unsatisfactory casting. BAPP produced a viscous, reactive mixture with satisfactory properties. JEFFAMINE® D-230 was slow to react, but produced overall good properties. JEFFAMINE® EDR-148 again produced superior properties in several areas. The formulation exhibited low viscosity, was quite reactive, and had outstanding impact resistance and good adhesion properties.

EXAMPLE 2

    ______________________________________                                         Properties: Epoxy Resin/Blocked Isocyanate Prepolymer                          Blend (80/20 pbw) Cured With Various Amines                                    6297                                                                           Formulation:                                                                   15A                                                                            62C                                                                            19C                                                                            6A                                                                             ______________________________________                                         Liquid epoxy resin                                                                             80      80      80     80                                      (EEW ≈ 185)                                                            Blocked prepolymer.sup.1                                                                       20      20      20     20                                      3,3'-Dimethyl-4,4'-diamino-                                                                    27      --      --     --                                      cyclohexylmethane.sup.2                                                        Bis(3-Aminopropyl)-                                                                            --      23      --     --                                      piperazine (BAPP)                                                              Polyoxypropyleneamine                                                                          --      --      26     --                                      (MW ≈ 230).sup.3                                                       Triethylene glycol                                                                             --      --      --     17                                      diamine.sup.4                                                                  Exothermic Properties:                                                         Brookfield viscosity,                                                                          10000   5000    2500   2000                                    cps, ≈23° C.                                                    Gel time, mins. 70-75   18.5    200.sup.7                                                                             17.9                                    (200 g mass)                                                                   Peak exothermic 129.2   208.5   80     220.2                                   temperature, °C.                                                        Time to peak temper-                                                                           102.0   21.0    350    26.0                                    ature, mins.                                                                   Properties of Cured                                                                            6                                                              1/8 in. Castings.sup.5:                                                        Rheometrics impact,     --      89     144                                     total energy, in-lbs.                                                          Tensile strength, psi   7000    6200   6400                                    Tensile modulus, psi    533000  269000 306000                                  Elongation at break, %  6.6     7.5    5.7                                     Flexural strength, psi  10800   10300  10100                                   Flexural modulus, psi   310000  311000 307000                                  HDT, °C., 264 psi/66 psi                                                                        53/56   44/46  44/47                                   Adhesive Properties.sup.5:                                                                     8                                                              Tensile shear strength, psi                                                                            2300    2800   3000                                    T-peel strength, pli    7.2     5.3    6.4                                     ______________________________________                                          .sup.1 Polyoxypropylene polyol/TDI reaction product block with                 nonylphenol; Desmocap 11A (Mobay Chemical Corp.)                               .sup.2 Laromin C260 (BASF)                                                     .sup.3 JEFFAMINE ® D230                                                    .sup.4 JEFFAMINE ® EDR148                                                  .sup.5 Cured 14 days, ≈23° C.                                   .sup.6 Casting brittle; without strength. Shattered on removal from mold       .sup.7 Time to reach 10,000 cps .sup.8 Brittle adhesive bond. Fractured        before testing. No properties could be determined.                             .sup.8 Brittle adhesive bond. Fractured before testing. No properties          could be determined.                                                     

In Example 3, containing 30% blocked isocyanate, Laromin C-260 again formed a viscous mixture of low reactivity with the blend. However, using this percentage of prepolymer, brittleness of the casting had decreased so that properties could be obtained. A degree of brittleness remained, as evidenced by the casting's elongation, impact and peel strength. The highly reactive amine, BAPP, formed a viscous mass which was difficult to process. No properties could be obtained with this formulation. Either of the polyetheramines, JEFFAMINE® D-230 or JEFFAMINE® EDR-148, produced flexible castings with superior properties of elongation, impact and peel strength.

JEFFAMINE® D-230, even in the presence of 30% blocked isocyanate, was slow to react, indicating usage in application areas such as filament winding, potting and encapsulation where an extended working time is necessary. Rapid reaction was shown by the formulation cured with JEFFAMINE® EDR-148. Such systems would find other applications where rapidity of reaction is required, i.e. reaction injection molding.

EXAMPLE 3

    ______________________________________                                         Properties: Epoxy Resin/Blocked Isocyanate Prepolymer                          Blend (70/30 pbw) Cured With Various Amines                                    6297                                                                           Formulation:                                                                   15B                                                                            62D                                                                            19D                                                                            6B                                                                             ______________________________________                                         Liquid epoxy resin                                                                             70      70      70     70                                      (EEW ≈ 185)                                                            Blocked prepolymer.sup.1                                                                       30      30      30     30                                      3,3'-Dimethyl-4,4'-diamino-                                                                    26      --      --     --                                      cyclohexylmethane.sup.2                                                        Bis(3-Aminopropyl)-                                                                            --      19      --     --                                      piperazine (BAPP)                                                              Polyoxypropyleneamine                                                                          --      --      23     --                                      (MW ≈ 230).sup.3                                                       Triethylene glycol                                                                             --      --      --     14                                      diamine.sup.4                                                                  Exothermic Properties:                                                         Brookfield viscosity,                                                                          19000   15000   ≈4500                                                                         3800                                    cps, ≈23° C.                                                    Gel time, mins. ≈75                                                                            15.7    ≈108                                                                          9.5                                     (200 g mass)                                                                   Peak exothermic 96      187.5   57     188.5                                   temperature, °C.                                                        Time to peak tem-                                                                              114     21.5    198    24.0                                    perature, mins.                                                                Properties of Cured     6                                                      1/8 in. Castings.sup.5:                                                        Rheometrics impact,                                                                            4               263    160                                     total energy, in-lbs.                                                          Tensile strength, psi                                                                          2100            3600   3900                                    Tensile modulus, psi                                                                           224000          173000 182000                                  Elongation at break, %                                                                         1.0             47     21.7                                    Flexural strength, psi                                                                         7850            6300   6900                                    Flexural modulus, psi                                                                          222000          189000 189000                                  HDT, °C., 264 psi/66 psi                                                                45/49           38/42  40/43.5                                 Adhesive Properties.sup.5:                                                     Tensile shear strength, psi                                                                    2200            2200   2600                                    T-peel strength, pli                                                                           1.8             5.7    7.7                                     ______________________________________                                          .sup.1 Polyoxypropylene polyol/TDI reaction product block with                 nonylphenol; Desmocap 11A (Mobay Chemical Corp.)                               .sup.2 Laromin C260 (BASF)                                                     .sup.3 JEFFAMINE ® D230                                                    .sup.4 JEFFAMINE ® EDR148                                                  .sup.5 Cured 14 days, ≈23° C.                                   .sup.6 Gelled while transferring to mold. No properties were determined. 

Example 4 demonstrates curing with an unhindered polyetheramine (JEFFAMINE® EDR-148 from Texaco Chemical Company) which resulted in rapid curing of relatively low viscosity systems. Formulations which contained >39% blocked prepolymer were quite reactive and difficult to process. However, properties of formulations containing only small amounts of prepolymer were considerably improved in several important areas over a formulation containing no prepolymer. Rheometrics impact values were vastly improved with just the smallest amounts of prepolymer present. Strength and modulus values declined with increased prepolymer while elongation and adhesion values increased. Toughening of the product as shown with small amounts of prepolymer was accomplished with retention of a high percentage of original physical properties.

EXAMPLE 4

    __________________________________________________________________________     Properties: Curing Epoxy Resin/Blocked Isocyanate                              Prepolymer Blends With Triethylene Glycol Diamine                              (JEFFAMINE ® EDR-148)                                                                    6357                                                             Formulation:  58C                                                              4A                                                                             4B                                                                             6A                                                                             6B                                                                             6C                                                                             6D                                                                             __________________________________________________________________________     Epoxy resin.sup.1 /Blocked                                                     prepolymer.sup.2, pbw                                                          100/0         100 --  --  --  --  -- --                                        95/5          --  100 --  --  --  -- --                                        90/10         --  --  100 --  --  -- --                                        80/20         --  --  --  100 --  -- --                                        70/30         --  --  --  --  100 -- --                                        60/40         --  --  --  --  --  100                                                                               --                                        50/50         --  --  --  --  --  -- 100                                       JEFFAMINE ® EDR-148                                                                      20  20  18  17  14  12 11                                        Brookfield viscosity,                                                                        700 1000                                                                               1200                                                                               2000                                                                               3800                                                                               6800                                                                              10000                                     cps, 25° C.                                                             Gel time, mins.                                                                              55.5                                                                               51.6                                                                               36.4                                                                               17.9                                                                               9.5 4  4                                         (200 g mass)                                                                   Peak exothermic                                                                              242.0                                                                              237.8                                                                              236.5                                                                              220.2                                                                              188.5                                                                              155.8                                                                             138.2                                     temp., °C.                                                              Time to peak tem-                                                                            63.0                                                                               57.0                                                                               39.7                                                                               26.0                                                                               24.0                                                                               22.5                                                                              25.0                                      perature, mins.                                                                Properties of cured               4  4                                         1/8 in. castings.sup.3 :                                                       Rheometrics impact,                                                                          11  158 126 144 160                                              total energy, in-lbs.                                                          Tensile strength, psi                                                                        9600                                                                               8500                                                                               8800                                                                               6400                                                                               3900                                             Tensile modulus, psi                                                                         441000                                                                             406000                                                                             414000                                                                             306000                                                                             182000                                           Elongation at break, %                                                                       3.4 3.0 3.2 5.7 21.7                                             HDT, °C., 264 psi/66 psi                                                              51/53                                                                              51/52                                                                              48/50                                                                              44/47                                                                              40/43.5                                          Adhesive Properties.sup.3                                                      Tensile shear strength,                                                                      1400                                                                               1900                                                                               3050                                                                               3000                                                                               2600                                                                               1800                                                                              1200                                      psi                                                                            T-peel strength, pli                                                                         0.9 5.1 9.4 6.4 7.7 13.0                                                                              25.4                                      __________________________________________________________________________      .sup.1 Liquid epoxy resin of equivalent weight 185-192                         .sup.2 Blocked isocyanate prepolymer; Desmocap 11A, Mobay Chemical Co.         .sup.3 Cured 14 days, 25° C.                                            .sup.4 Material gelled while degassing; could not prepare samples        

Example 5 demonstrates the use of Laromin C-260 as a curative of similar formulations which formed viscous mixtures that were difficult to process and did not cure rapidly. Castings cured with Laromin C-260 were brittle and without strength. Large amounts of prepolymer were necessary to reduce brittleness to an acceptable, testable level. Formulations which contained these large amounts of prepolymer were extremely viscous and quite difficult to process BAPP (Example 6) also formed brittle castings with small amounts of prepolymer present but cured so rapidly with larger amounts of prepolymer so that processing was difficult. JEFFAMINE® D-230 (Example 7) reacted slowly with epoxy/prepolymer blends in contrast to rapid curing with EDR-148. Properties obtained on curing with D-230 were satisfactory. Enhancement of impact and adhesion properties developed with large amounts of prepolymer present in the formulation.

EXAMPLE 5

    __________________________________________________________________________     Properties: Curing Epoxy Resin/Blocked Isocyanate                              Prepolymer Blends With 3,3'-Dimethyl-4-4,4'-Diamino-                           cyclohexylmethane                                                                           6297-                                                             Formulation: 97B                                                                               17A                                                                               17B                                                                               15A 15B 15C                                                                               15D                                           __________________________________________________________________________     Epoxy resin.sup.1 /Blocked                                                     prepolymer.sup.2, pbw                                                          100/0        100                                                                               -- -- --  --  -- --                                            95/5         -- 100                                                                               -- --  --  -- --                                            90/10        -- -- 100                                                                               --  --  -- --                                            80/20        -- -- -- 100 --  -- --                                            70/30        -- -- -- --  100 -- --                                            60/40        -- -- -- --  --  100                                                                               --                                            50/50        -- -- -- --  --  -- 100                                           3,3'-Dimethyl(4,4'-diamino-                                                                 34 32 30 27  26  24 20                                            cyclohexylmethane.sup.3                                                        Brookfield viscosity,                                                                       7000  8500                                                                              10000                                                                              19000  31000                                         cps, 25° C.                                                             Gel time, mins.                                                                             210   90 70-75                                                                              75     6                                             (200 g mass)                                                                   Peak exothermic                                                                             127   115                                                                               129.2                                                                              96                                                   temp., °C.                                                              Time to peak temper-                                                                        240   190                                                                               102 114                                                  ature, mins.                                                                   Properties of cured                                                                         5  5  5  5       7  7                                             1/8 in. castings.sup.4 :                                                       Rheometrics impact,       4                                                    total energy, in-lbs.                                                          Tensile strength, psi     2100                                                 Tensile modulus, psi      224000                                               Elongation at break, %    1.0                                                  HDT, °C., 264 psi/66 psi                                                                          45/49                                                Adhesive Properties.sup.4                                                      Tensile shear strength,   2200                                                                               2600                                                                              1600                                          T-peel strength, pli      1.8 6.6                                                                               6.5                                           __________________________________________________________________________      .sup.1 Liquid epoxy resin of equivalent weight 185-192                         .sup.2 Blocked isocyanate prepolymer; Desmocap 11A, Mobay Chemical Co.         .sup.3 Laromin C260; BASF Corp., Chemicals Division                            .sup.4 Cured 14 days, 25° C.                                            .sup.5 Brittle castings, without strength. Could not determine properties      .sup.6 Viscous mixture; could not determine time of gellation.                 .sup.7 Material gelled while degassing; could not prepare castings.      

EXAMPLE 6

    ______________________________________                                         Properties: Curing Epoxy Resin/Blocked Isocyanate                              Prepolymer Blends With Bis(3-Aminopropyl)Piperazine                            (BAPP)                                                                                       6297                                                             Formulation:  97A     62A    62B   62C   62D                                   ______________________________________                                         Epoxy resin.sup.1 /Blocked                                                     prepolymer.sup.2, pbw                                                          100/0         100     --     --    --                                          95/5          --      100    --    --    --                                    90/10         --      --     100   --    --                                    80/20         --      --     --    100   --                                    70/30         --      --     --    --    100                                   Bis(3-Aminopropyl)                                                                           27      25     23    23    19                                    Piperazine                                                                     Brookfield viscosity,                                                                        2200    2300   4300  5000  15000                                 cps, 25° C.                                                             Gel time, mins.                                                                              59.6    29.5   30.0  18.5  15.7                                  (200 g mass)                                                                   Peak exothermic                                                                              222.5   223.5  219.5 208.5 187.5                                 temp., °C.                                                              Time to peak tem-                                                                            65.6    36.5   39.0  21.0  21.5                                  perature, mins.                                                                Properties of cured   5                  6                                     1/8 in. castings.sup.3 :                                                       Rheometrics impact,                                                                          6       2      4     --                                          total energy, in-lbs.                                                          Tensile strength, psi                                                                        1300    8100   7000                                              Tensile modulus, psi                                                                         536000         344000                                                                               533000                                      Elongation at break, %                                                                       2.3            2.78  6.6                                         HDT, °C., 264 psi/66 psi                                                              --             57/58 53/56                                       Adhesive Properties.sup.3                                                      Tensile shear strength,                                                                      4       800    1300  2300  2700                                  psi                                                                            T-peel strength, pli                                                                         4       4      3.5   7.2   7.2                                   ______________________________________                                          .sup.1 Liquid epoxy resin of equivalent weight 185-192                         .sup.2 Desmocap 11A, Mobay Chemical Company                                    .sup.3 Cured 14 days, 25° C.                                            .sup.4 Sample broke before testing  no properties were determined.             .sup.5 Casting was brittle and without strength  could not determine           properties.                                                                    .sup.6 Gelled while pouring into mold  no properties were determined.    

EXAMPLE 7

    ______________________________________                                         Properties: Curing Epoxy Resin/Blocked Isocyanate                              Prepolymer Blends With a Hindered Polyether Diamine                            (JEFFAMINE ® D-230)                                                                     6357-   6297-                                                     Formulation: 58D     19A     19B   19C   19D                                   ______________________________________                                         Epoxy resin.sup.1 /Blocked                                                     prepolymer.sup.2, pbw                                                          100/0        100     --      --    --                                          95/5         --      100     --    --    --                                    90/10        --      --      100   --    --                                    80/20        --      --      --    100   --                                    70/30        --      --      --    --    100                                   JEFFAMINE ®                                                                D-230                                                                          Brookfield viscosity,                                                                       2200    2300    4300  5000  15000                                 cps, 25° C.                                                             Gel time, mins.                                                                             280.sup.4                                                                              312.sup.4                                                                              258.sup.4                                                                            200.sup.4                                                                            108                                   (200 g mass)                                                                   Peak exothermic                                                                             64      32      33    80    57                                    temp., °C.                                                              Time to peak temper-                                                                        396     366     414   350   198                                   ature, mins.                                                                   Properties of cured                                                            1/8 in. castings.sup.3 :                                                       Rheometrics impact,                                                                         12      19      15    89    263                                   total energy, in-lbs.                                                          Tensile strength, psi                                                                       6600    9000    8700  6200  3600                                  Tensile modulus, psi                                                                        417000  430500  408000                                                                               269000                                                                               173000                                Elongation at break,                                                                        1.5     2.5     3.3   7.5   47                                    HDT, °C.,                                                                            43/46   48/48   44/47 44/46 38/42                                 264 psi/66 psi                                                                 Adhesive Properties.sup.3                                                      Tensile shear                                                                               900     1100    1400  2800  2200                                  strength, psi                                                                  T-peel strength, pli                                                                        3.9     4.6     5.1   5.3   5.7                                   ______________________________________                                          .sup.1 Liquid epoxy resin of equivalent weight 185-192                         .sup.2 Desmocap 11A, Mobay Chemical Company                                    .sup.3 Cured 14 days, 25° C.                                            .sup.4 Time to reach viscosity of 10,000 cps                              

What is claimed is:
 1. A composition cured at ambient temperatures comprising a blend of 70% to 90% of a epoxy resin with 10% to 30%, by weight of the total epoxy resin/blocked isocyanate prepolymer blend, of a polyoxyalkylene polyol/isocyanate prepolymer blocked with an alkylated phenol and an effective curing amount of a polyetherpolyamine selected from the group consisting of a polyoxypropylenediamine having the formula:

    H.sub.2 NCH(CH.sub.3)CH.sub.2 [OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2

wherein x is a number having an average value of 2 to 3 and an amine terminated polyethylene glycol having the formula:

    H.sub.2 N--(CH.sub.2 CH.sub.2 --O).sub.x CH.sub.2 CH.sub.2 NH.sub.2

where x=2.
 2. The composition of claim 1 wherein the polyetherpolyamine has the formula:

    H.sub.2 N--CH.sub.2 CH.sub.2 --O--CH.sub.2 CH.sub.2 --O--CH.sub.2 CH.sub.2 NH.sub.2.


3. A process for curing a blend of 70% to 90% of a epoxy resin and 10% to 30%, by weight of the total epoxy resin/blocked isocyanate prepolymer blend, of a polyoxyalkylene polyol/isocyanate prepolymer blocked with an alkylated phenol which comprises adding to the blend an effective curing amount of a polyetherpolyamine selected from the group consisting of a polyoxypropylenediamine having the formula:

    H.sub.2 NCH(CH.sub.3)CH.sub.2 [OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2

wherein x is a number having an average value of 2 to 3 and an amine terminated polyethylene glycol having the formula:

    H.sub.2 N--(CH.sub.2 CH.sub.2 --O).sub.x CH.sub.2 CH.sub.2 NH.sub.2

where x=2 and curing at ambient temperatures.
 4. The process of claim 3 wherein the polyetherpolyamine has the formula:

    H.sub.2 N--CH.sub.2 CH.sub.2 --O--CH.sub.2 CH.sub.2 --O--CH.sub.2 CH.sub.2 NH.sub.2.


5. A composition cured at ambient temperatures comprising:70-95 parts by weight of a epoxy resin having an epoxy equivalent weight of about 185; 5-30 parts by weight of a polyoxyalkylene polyol/isocyanate prepolymer blocked with an alkylated phenol; and a curing amount of amine terminated triethylene glycol. 